ribosomes can recognize sequence of translative protein-that's got a signal sequence. Tell ribosome to dock at specific place in ER and docking mechanism allows for translocation to middle of docking station and lumen of ER (secreted) or membrane protein to be released to membrane

SRP has RNA that recognizes a.a.s, halts translation, brings it to ER (receptor), and docks it to porin and translation resumes, protein snakes into lumen, signal cut with signal peptidase. Chaperone BiP drags it in and folds it